1. Field of the Invention
This invention relates to management and viewing of medical images and, more particularly, to systems and methods of tracking which portions of three dimensional imaging volumes have been displayed using predetermined display parameters.
2. Description of the Related Art
Medical imaging is increasingly moving into the digital realm. This includes imaging techniques that were traditionally analog, such as mammography, x-ray imaging, angiography, endoscopy, and pathology, where information can now be acquired directly using digital sensors, or by digitizing information that was acquired in analog form. In addition, many imaging modalities are inherently digital, such as MRI, CT, nuclear medicine, and ultrasound. Increasingly these digital images are viewed, manipulated, and interpreted using computers and related computer equipment. Accordingly, there is a need for improved systems and methods of viewing and manipulating these digital images.
For projection modalities like mammography and radiography, information may be represented in digital images in the form of a two dimensional array of pixels (picture elements). Other techniques are capable of creating cross sectional views of the body, such as magnetic resonance imaging (MRI), computed tomography (CT), and positron emission computed tomography (PET). With these techniques, the information in an image represents a two-dimensional slice of the body, with each pixel in the image representing information from a small volume in space, a voxel (volume element). In a typical imaging exam (“scan”) using these modalities, a series of parallel images are acquired through the body. The information in this series of images therefore represents a 3D volume of space or imaging volume. In addition, a three-dimensional imaging volume may be created from a set of nonparallel images as well. It is also possible to perform a three-dimensional acquisition directly with some modalities. Thus, the image volume may be generated by a device that creates a 3D data set.
While a radiologist or physician interpreting such an imaging volume might choose to view the acquired images, the plane in which the images were acquired may not be optimal for accurate and efficient analysis and interpretation of the scan. For example, imaging might be performed in the axial plane with the patient asymmetrically positioned in the scanner. The resulting images would therefore not be in the axial plane with respect to the patient's anatomy. In that case, a new set of axial images would be desired that were in the axial plane with respect to the patient's anatomy. Alternatively, structures of interest might be best evaluated in other planes, such as coronal, sagittal or oblique planes.
A reader may choose to view the information in planes that differ from the plane in which the images were originally acquired as a supplement or substitute for viewing the original images. Those of skill in the art will recognize that given the 3D imaging volume created by the original images from the imaging device, a new set of 2D images that slice up the imaging volume along other axes using multiplanar reformatting (MPR) may be created. The reformatting could be used to create a series of images in another axis prior to viewing or the viewer might choose to interactively create new views in real time as part of his analysis of the information.
No matter how the reader chooses to view the imaging volume acquired by the scan, all the acquired relevant information in the imaging volume should be viewed. Currently available systems for viewing imaging volumes do not provide a mechanism for tracking which portions of the imaging volume, such as which voxels of the imaging volume, have been displayed on a display device. Thus, the viewer must independently determine which portions of an imaging volume have been viewed. As those of skill in the art will recognize, requiring the viewer to determine when all relevant portions of an imaging volume have been viewed introduces the possibility that portions of the imaging volume are not viewed and, thus, features and/or abnormalities expressed in the unviewed portions may not be detected. Systems and methods for tracking and alerting a viewer of an imaging volume which portions of the imaging volume have been viewed are desired.